Phthalocyanine type pigments are sharp blue pigments having high fastness, and have conventionally been used as blue coloring agents for various printing inks, paints and plastics. Generally employed as a phthalocyanine type blue pigment is a copper phthalocyanine pigment obtainable by condensing phthalic anhydride using copper as a central metal. This pigment is polymorphic. Its α-crystalline form is unstable (metastable) in an organic solvent or under heat, undergoes a crystalline transformation, and also changes in color from a reddish blue color to a greenish blue color. On the other hand, its β-crystalline form is a stable crystalline form, but has a greenish blue color.
As a method for preventing such a change in crystallinity, it has been proposed to incorporate a copper alkylphthalocyanine, which contains one or more alkyl groups or cycloalkyl groups, at from 10 to 1.5 mole % in the copper phthalocyanine pigment. The resulting copper phthalocyanine pigment composition is described to have resistance to recrystallization and also resistance to flocculation and therefore to be suited as a blue color for various paints, printing inks, high-molecular materials, fibers, and the like (Patent Document 1).
It is also described that a composition of a copper phthalocyanine containing from 0.1 to 3 methyl groups on average per phthalocyanine skeleton exhibits anti-recrystallization properties during its storage in the presence of a solvent, and therefore, is suited for use in paints and inks and is also suited as a pigment for coloring plastic materials to be used at elevated temperatures (Patent Document 2).    Patent Document 1: JP-A-49-81436    Patent Document 2: JP-A-7-76662
However, laser copying machines, laser printers and inkjet printers have become widespread for office use and personal use in recent years, and moreover, digital printers have been recently finding utility as small business printers in combination with large offset printers. Conventionally, copper phthalocyanine blue pigments have been employed with praise as blue pigments for use as cyan colors in information recording materials such as cyan toners for laser printers and color copying machines and also in cyan inks for inkjet printers. There is, however, an increasing desire for expressions in a still broader color gamut as color printing expressions of printed characters and images, leading to an outstanding desire for a blue pigment having, as a cyan color, a more greenish color than β-copper phthalocyanine pigments.
As blue pigments for the formation of blue pixels on image display means such as color filters, reddish blue ε-copper phthalocyanine pigments are used. However, these pigments are a little unstable in solvents or under heat, and therefore, require additives (pigment derivatives) for inhibiting crystalline transformation and crystal growth of the pigments.
By substituting 1 to 2 halogen atoms such as chlorine atoms on each phthalocyanine skeleton, the transformational growth properties of crystals of the pigment are inhibited. As a result, however, its color tone changes to a greenish blue color. The above-described halogenated copper phthalocyanine is, therefore, insufficient as an additive (pigment derivative) to be incorporated in a reddish blue pigment. Accordingly, there is an outstanding desire for a phthalocyanine type pigment, which is stable in organic solvents and under heat, does not undergo much crystalline transformation, has a reddish blue color, and does not undergo much changes in color.